Looking forward — and back — for phosphorous fertility planning

As you sit down to finalize fertility plans for the 2020 growing season, do you look at a one, two, or five-year window when determining phosphorus rates?

Jeremy Boychyn, agronomy research extension specialist with the Alberta Wheat and Barley Commissions, says it’s time we really start to consider looking at multiple years at a time when it comes to phosphorus application.

“If you go to any presentation anywhere that’s talking about fertility and fertilizer in Western Canada and even in the U.S., there are concerns about phosphorous loss or depletion, where we’re not getting enough back into our soil compared to what we’re removing with our crops,” says Boychyn.

“What seems to happen is we look at phosphorous on a year-by-year basis, where we’re asking, ‘OK, what’s my yield potential going to be, how much phosphorous do I need for that?’ You look at something like wheat, where every ten bushels you are maybe pulling something off like five pounds of phosphorous. If you’re doing a 50-bushel crop, you’re pulling off potentially in that 30-pound range of phosphorous. Are you putting that much phosphorous down?”

If the answer to that question is no, you will have a soil phosphorous deficit, and one that will continue to grow every year, despite some producers thinking they are “resetting” at the beginning of the season. Which is why Boychyn has been encouraging producers to look at an eight-year plan — four years forward and four years back.

“The reason you do that is because you track how much yield you’ve had over the past four years, and how much phosphorus has been removed from that yield, leading up to this year. And that’ll give you a positive or a deficit. And then you plan the next four years based on your positive or deficit from the previous four years,” he says.

For example, if over the past four years you pulled out 20 more pounds of phosphorous than what you put in, over the next four years you want to plan to compensate for that. By keeping track, you know you are in a building mode for phosphorous or you know you’re in a maintenance mode. As well, you can check out the Alberta Agriculture and Forestry Grains, Forage, and Straw Nutrient Use Calculator.

To learn some tips on building a phosphorous plan, and more on nutrient planning, check out the conversation between Kara Oosterhuis and Jeremy Boychyn, filmed at FarmTech in Edmonton, Alberta:

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